Volume and location of screen-detected lung nodules associated with lung cancer within two-year follow-up: Post hoc analysis from the UK Lung Cancer Screening (UKLS) trial

INTRODUCTION: Follow-up of radiologically suspicious lung nodules from screening programs remains complex and unstandardized. This study analyses distribution and characteristics of solid and part-solid non-calcified nodules ≥100 mm 3 and non-solid nodules ≥8 mm detected at baseline in the UK Lung cancer Screening (UKLS) trial, with insights into their relationship to screen-detected lung cancers.

METHODS: UKLS participants with baseline indeterminate and positive lung nodules were included. Nodule location was categorized by lobe and by attachment: intraparenchymal, juxta pleural or pleural-based. Solid and part-solid were classified based on semi-automated volume: 100-300 mm 3 and ≥300 mm 3, and non-solid nodules based on diameter ≥8 mm. This measurement approach aligns with UKLS protocol and the British Thoracic Society (BTS) guideline. Their relationship to screen-detected lung cancer was based on histological outcomes after a 2-year follow-up period.

RESULTS: 279 UKLS participants with 373 solid or part-solid lung nodules ≥100 mm 3 and 57 participants with 62 nonsolid nodules ≥8 mm were included. Among solid and part-solid nodules, 233 were 100-300 mm 3, with 39.5% in upper lobes and 72.5% intraparenchymal; 140 nodules were ≥300 mm 3, with 51.4% in upper lobes and 53.6% intraparenchymal. Nodules ≥300 mm 3 group were more likely to be in the upper lobes (OR 1.97 [95% CI 1.12-3.48]). Within 2 years, 34 solid or part-solid nodules were diagnosed as lung cancer, yielding a 2-year cancer probability of 9.1% (95% CI 6.6-12.5). The 2-year lung cancer probability was higher in nodules ≥300 mm 3 (RR 18.1, 95% CI 5.6-58.4; p < 0.001) and in upper lobe nodules (RR 2.7, 95% CI 1.3-5.5; p = 0.009).

CONCLUSION: Solid and part-solid nodules with volume ≥300 mm 3 were more often found in the upper lobes and were associated with a higher probability of lung cancer within a two-year follow-up period.